Inert landfill, Oxfordshire. Review of Hydrogeological risk assessment

This landfill was originally permitted in 2004. The permit conditions required a written review of the hydrogeological risk assessment completed in support of the permit application, 3.5 years after the permit was issued. Hafren Water was commissioned to undertake this work in early 2008. The information obtained during the initial stages of the work indicated that a complete revision of the original conceptual model was required.
Additional information on the site geology was obtained from nearby quarries and during two site visits. As a result a new conceptual model of the site hydrogeology and the interaction between the landfill and groundwater system was devised. All the available groundwater monitoring data was reviewed and analysed in the context of the revised conceptual model. A report was submitted to the Environment Agency, documenting all the monitoring data and describing the updated conceptual understanding. Recommendations were included for a revised monitoring scheme, including new boreholes, which would take into account the new conceptual model. Discussions are still ongoing with the Environment Agency with regard to further work required.

Non-hazardous landfill near Warrington. Complex quantitative risk assessment modelling

Hydrogeological risk assessment work was undertaken in support of an Appeal against the refusal of a PPC Permit Application undertaken by other consultants. Detailed discussions were held with the Agency who had lost confidence in the operator and their consultants regarding the hydrogeological understanding for the site. The site, which had been previously operated as an industrial & commercial landfill receiving some special wastes, is underlain by sandstone, siltstone and mudstone, all overlain by various glacial deposits. A complex history of mineral extraction and variation in landfill engineering at the site led to the need for further site investigation work to establish the groundwater flow patterns in the various permeable strata and the lateral extent of sand and gravel horizons within the superficial deposits.

Waste face

RAM Model

Following detailed data assessment, the geology of the site was reinterpreted and the conceptual model completely revised.  Conceptual model reporting and full probabilistic modelling was undertaken in support of a new hydrogeological risk assessment, which formed the basis of a new PPC Permit application.  Following in-depth discussions with the Environment Agency and site visits, they agreed with our conceptualisation of the site and hydrogeological risk assessment and a Permit has now been granted. 

Inert landfill, Cambridgeshire. Hydrogeological risk assessment

he landfill is located on a Major Aquifer (Chalk), close to the edges of the outer source protection zones for two public water supplies. A qualitative hydrogeological risk assessment had already been completed as part of a PPC Permit Application, but the Environment Agency felt this was insufficient given the location on a Major Aquifer. Hafren Water was retained to undertake a quantitative risk assessment to further support the permit application. Additional data requirements were identified and a limited site investigation was undertaken by the client to provide data for a source term for the risk assessment. A report comprising an updated conceptual model, outputs from the quantitative risk assessment and proposals for groundwater monitoring was submitted to the Environment Agency. The assessment concluded that the site did not pose a risk to groundwater quality, an outcome which was accepted by the Environment Agency. A permit is due to be issued imminently.

Non-hazardous landfill in Essex. Addressing non-compliant leachate levels

The landfill site had leachate levels that exceeded the maximum specified in the Waste Management Licence (WML). A previous investigation had indicated that, for a variety of reasons, these specified levels were not attainable. Hafren Water was retained to undertake a hydrogeological risk assessment to establish risks to the environment from the elevated leachate levels. 

Waste face

Hazardous landfill in Cambridgeshire. PPC Application

The landfill is located on a Major Aquifer (Chalk), close to the edges of the outer source protection zones for two public water supplies. A qualitative hydrogeological risk assessment had already been completed as part of a PPC Permit Application, but the Environment Agency felt this was insufficient given the location on a Major Aquifer. Hafren Water was retained to undertake a quantitative risk assessment to further support the permit application. Additional data requirements were identified and a limited site investigation was undertaken by the client to provide data for a source term for the risk assessment. A report comprising an updated conceptual model, outputs from the quantitative risk assessment and proposals for groundwater monitoring was submitted to the Environment Agency. The assessment concluded that the site did not pose a risk to groundwater quality, an outcome which was accepted by the Environment Agency. A permit is due to be issued imminently.. 

Hydrogeological conceptual model

Agreement was achieved with the Environment Agency regarding the required level of assessment and appropriate modelling package. A new robust conceptual model was developed and agreed with the Agency. Subsequent risk assessment entailed full probabilistic quantitative modelling, using RAM software, which was undertaken to the satisfaction of the Agency, who agreed that no substantive hydrogeological issues remained with the site. To date other issues have prevented the site obtaining a PPC permit.

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